SvelteKit app on azure app service

Hello @Ihtisham Mushtaq ,

You can deploy a SvelteKit frontend to Azure App Service (Linux), but there are some important considerations when working with the @sveltejs/adapter-node (Node adapter).

Typically, the Node adapter creates an Express or Polka server to serve your app. This setup works well locally, but on Azure App Service (Linux), which uses a containerized environment, your app needs to meet specific requirements.

Key items to verify:

Build step prior to deployment

Azure does not automatically execute npm run build unless set up to do so. You should:

• Run npm run build during deployment, such as in GitHub Actions, Azure Pipelines, or Oryx build.
• Make sure .output/ (or build/, based on your configuration) is part of the deployed package.

Proper startup command

Once you have built your app using adapter-node, you usually start it with

node build/index.js

For App Service, you need to specify how it should start.

• Go to Azure Portal → App Service → Configuration → General Settings → Startup Command and enter the required command.

npm run start

• (Make sure your package.json includes "start": "node build/index.js").

Port binding

Azure provides a PORT environment variable that your server needs to use. By default, SvelteKit with adapter-node listens on port 3000. Modify your server.js (or index.js) to use process.env.PORT

const { handler } = require('./handler.js');
const { createServer } = require('http');
const port = process.env.PORT || 3000;
createServer(handler).listen(port, () => {
  console.log(`Server running on port ${port}`);
});

Recent versions of adapter-node handle this automatically, but please review your generated build/index.js to confirm.

Always On

For Basic or Paid App Service Plans, enable Always On to prevent Azure from unloading your container during idle periods.

Node version

Ensure that App Service is set to the correct Node version (Configuration → General Settings → Stack Settings). SvelteKit typically needs Node 18 or higher.

@Anonymous Thank you for the response, I have managed to stabilize the app service but still facing an issue, the app service where i have deployed the code was stopped for long time and i have started it recently and deployed sveltekit there, now i am getting domain resolution issues, i feel it might be because of app service being down for long time. I connected with some azure support team but didnt get proper response, they want to check it with their networking team.
even if there is some issue in my code i should get 500 error 503 or something but not the domain resolution issue. Any suggestions on this